Answer: B. attendance
Definition:
Attend: A verb that means be present at some event.
Attendance: A noun that means the state of being present.
Register: A noun or a verb that represents an official record or the action of recording.
Regist: It is not a word
Explanation:
"My teacher takes __________ at 7:30 a.m everyday."
This sentence might mean that the teacher needs to note down who is present and who is not. Also, the sentence shows a sense of [takes something], therefore, the blank should be a noun.
From the clues we get, "a noun" and "who is present and who is not", the word should be "attendance".
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